1. Field of the Invention
This invention relates to a cover for a communications port, and more particularly to a protective cover for a communications jack and a battery compartment. The invention also relates to an electrical switching device having a communications port, a battery compartment, and a cover for the communications port and battery compartment.
2. Background of Information
Electrical switching devices include, for example, circuit switching devices, circuit breakers and circuit interrupters. Circuit breakers, which are well-known in the art, are generally used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload fault or a relatively high level short circuit condition. Molded case circuit breakers, for example, include at least one pair of separable contacts which are operated either manually by way of a handle disposed on the outside of the case or automatically by way of an internal digital trip unit in response to an overcurrent condition. Examples of molded case circuit breakers are disclosed in U.S. Pat. No. 4,656,444; 4,679,018; 4,827,369; and 4,963,846.
Circuit interrupters are electrically operated switches used for controlling motors and other types of electrical loads. Circuit interrupters include, for example, contactors, motor starters, motor controllers and other electromechanical switching devices. Electromagnetic contactors, for example, include a plurality of movable electrical contacts which are brought into contact with a plurality of fixed electrical contacts to close the contactor. The movable electrical contacts are separated from the fixed contacts to open the contactor. A contactor with an overload protection relay system is called a motor starter. The purpose of the overload relay is to estimate the heat produced in the motor by line current and "trip" or stop the motor if the retained heat exceeds an acceptable level.
Some electrical switching devices include a communications link for communication with a remote monitoring unit or a local programming device. For example, as described in U.S. Pat. No. 5,315,531 which is hereby incorporated by reference, individual energy monitoring units for associated circuit breakers are remotely linked to a central monitoring unit, such as a personal computer (PC), through a communications system. The communications system utilizes a simple two wire synchronous communication line which is daisy chained to the several energy monitoring units and the PC. The PC digitally addresses each of the energy monitoring units in a master-slave relationship for the purpose of gathering the data generated by each of such units for central processing and allocating energy consumption billing for the loads of the associated circuit breakers.
Otherwise, the circuitry of the energy monitoring unit may be integrated with the associated circuit breaker. The local programming device utilizes the same or a similar communications link as the remote monitoring unit in order to, for example, monitor energy consumption, determine the closed/opened/trip status of the circuit breaker, or modify pickup current factors and time factors of the digital trip unit.
The energy monitoring circuitry includes a custom Sure Plus integrated circuit chip (IC) described in U.S. Pat. No. 5,270,898 which is hereby incorporated by reference. This IC includes an analog to digital converter, a microprocessor and a communications interface by which the calculated energy consumed by the associated load is provided to the communications link through a communications port connector in the housing of the circuit breaker.
The digital trip unit is used with various frame sizes of circuit breakers. In addition, each of the frame sizes of circuit breakers with which the digital trip unit is compatible can be used to protect an electrical system in which the maximum continuous current permitted is less than or equal to the maximum continuous current permitted by the frame. In order to provide this information to the digital trip unit, a suitable, removable rating plug can be plugged into the digital trip unit. The rating plug contains a number of resistors which are keyed to the frame size, and which set the maximum or rated current for the particular installation. This rated current can be the maximum current allowed by the frame size or some smaller value.
An example of a circuit breaker with a rating plug is disclosed in U.S. Pat. No. 4,827,369 which is hereby incorporated by reference. The rating plug, as disclosed by this patent, also contains a battery which provides a three volt source of power. The digital trip unit is powered by current from the power circuit which is protected by the circuit breaker. When the circuit breaker trips and the current therethrough is interrupted, the power to the circuit breaker's microprocessor is normally interrupted. The three volt power provided by the battery of the rating plug is applied to a latch which stores trip status information and drives light emitting diodes (LEDs). In this manner, the LEDs remain energized following a trip and indicate the cause thereof.
U.S. Pat. No. 3,699,498 discloses a plug having a resiliently cantilevered latch which is mateable with miniature jacks in the handset and base of a telephone.
U.S. Pat. Nos. 4,311,883; 4,870,840; 4,964,284; 5,305,380; and 5,340,324 each disclose a dummy plug for a telephone socket or jack. In particular, U.S. Pat. No. 4,311,883 discloses a lock for a conventional telephone jack including a case and a plug having a cantilevered leaf spring. The leaf spring has corners outside the case that latch behind corners of the telephone jack socket opening when the plug is inserted therein. An unlocking mechanism is operable by a removable key to rotate a bolt within the case and depress the leaf spring therein in order to clear the corners of the socket opening and remove the plug therefrom.
U.S. Pat. No. 4,870,840 discloses a device for locking and unlocking an unused telephone socket opening. The device includes a plug which is attached to a casing of a sliding bolt lock. A sliding wedge is positioned under a leaf spring of the plug in order to prevent the plug from being removed from the socket opening whenever the wedge is locked in position by the bolt lock.
U.S. Pat. No. 4,964,284 discloses a device for locking and unlocking an unused telephone socket opening. The device includes a plug with a member which is movable by a barrel lock to engage or disengage a shoulder within the socket opening.
U.S. Pat. Nos. 5,305,380 and 5,340,324 similarly disclose locking plugs which are lockable within a conventional telephone socket opening and which are removable by a specialized tool or key.
U.S. Pat. No. 4,426,121 discloses a plug for masking switching contacts such as the terminal strips of telecommunication devices.
Whenever the communications port connector of the circuit breaker's communication link is unused and, hence, uncovered, such connector is subjected to dust and dirt from the surrounding industrial environment. Furthermore, the exposed electrical conductors of the communications connector may be subject to extreme voltage caused by electrostatic discharge (ESD) from, for example, maintenance personnel. With the exposed communications connector, such ESD may cause misoperation or damage to the communications link and/or the circuit breaker.
The battery for powering the status latch and external status LEDs of the circuit breaker may be held, separate from the rating plug, within a battery compartment in the face of the circuit breaker. Hence, following a trip, the rating plug may be removed and/or modified without disabling the status latch which continues to be powered by the battery. In the same manner as the exposed communications connector, the exposed battery compartment and battery are also subject to dust, dirt and ESD which may similarly cause damage or misoperation of the circuit breaker.